The invention relates to a charging device for a high-voltage battery of a motor vehicle, in particular a charging device installed in a motor vehicle, wherein the charging device is connected via a connection device to an alternating current network, wherein the connection device includes a residual current circuit switch incapable of detecting a residual current of at least one type of residual current, especially a DC residual current. In addition, the invention relates to a charging system with such a charging device and a connection device and a method for operating a charging system.
Motor vehicles are known that can also be operated with electrical energy, wherein electric vehicles receiving their propulsion energy solely from an electrical energy store, in particular a high-voltage battery, as well as hybrid vehicles obtained their propulsion energy in addition to the high-voltage battery from other energy sources, especially fossil fuels, have been disclosed.
In order to charge the high-voltage battery of such vehicle, it has been proposed to charge the high-voltage battery, in particular together with a low-voltage battery, from a conventional AC power supply, for example the residential network of the operator of the motor vehicle. While the additional low-voltage battery (also referred to as vehicle battery) has typically a voltage of about 12 V, the high-voltage battery has a higher voltage than the low-voltage battery, particularly a voltage above 50 V. High-voltage batteries with a battery voltage between 150 and 270 V are also known and in use. Thus, a special charging system is required to charge the high-voltage battery, preferably the high-voltage battery and the low-voltage battery. A charger, hereinafter also referred to as charging device, can be installed in the motor vehicle and may have a connector in which a mating connector with a charging cable can be inserted. The other side of the charging cable is connected, in particular via an electronics box and the like, with the AC network; optionally, a charging station with an appropriate charging cable may also be provided as connection to the AC mains.
Since this involves working with high-voltages and high currents, it is known to provide a residual current circuit breaker (FI switch) as protection against electric shock in the charging infrastructure, hereinafter referred to as connection device. Such a residual current circuit breaker can be installed, for example, in the charging station, in an electronics box in the charging cable or in the connector itself. It is also conceivable to already provide the FI-switch in or adjacent to a standard power outlet of the AC network. For cost and space considerations, it is common practice to use a type A residual current circuit breaker (FI type A). However, it has been observed that the type A residual current circuit breakers are unable to detect all residual currents that may occur in the charging device. These are so-called DC residual currents that would possibly be detectable with a type B residual current circuit breaker, which is however extremely large and expensive and is therefore rarely used.